1. Field of the Disclosure
The present disclosure generally relates to an organic light-emitting diode (OLED) display device, and more particularly, to an organic light-emitting diode (OLED) display device capable of displaying images with improved quality and a method of manufacturing the same.
2. Discussion of the Related Art
Recently, a slim, light-weight, flat panel display having low power consumption has been developed and applied to various technical fields.
In an organic light-emitting diode (OLED) display device, charges are injected into a light-emitting layer formed between a cathode electrode which is an electron injection electrode, and an anode electrode which is a hole injection electrode. The injected charges combine with holes in the light-emitting layer to form electron-hole pairs that emit light. The OLED display device can be formed on a flexible substrate such as a plastic substrate, provide excellent colors due to self-luminescence, and also minimize power consumption since it can be driven at a low voltage (below 10 V).
The OLED display device includes red, green, and blue light-emitting layers corresponding to, for example, red, green, and blue sub-pixel areas.
Hereinafter, a related art OLED display device will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view schematically showing a related art OLED display device.
As shown in FIG. 1, red, green, and blue sub-pixel areas R, G, and B are defined on a substrate 1.
Also, on the substrate 1, first electrodes 2 are formed in correspondence to the red, green, and blue sub-pixel areas R, G, and B.
A hole transport layer 3 is formed to cover the entire first electrodes 2.
On the hole transport layer 3, a red light-emitting layer 4, a green light-emitting layer 5, and a blue light-emitting layer 6 are respectively formed in correspondence to the red, green, and blue sub-pixel areas R, G, and B.
An electron transport layer 7 is formed on the red, green, and blue light-emitting layers 4, 5, and 6, and a second electrode 8 is formed on the electron transport layer 7.
Hereinafter, a method of manufacturing the related art OLED display device will be briefly described with reference to FIG. 2. FIG. 2 is a view schematically showing processes of manufacturing the related art OLED display device. FIG. 2 shows red, green, and blue sub-pixel areas R, G, and B, and red, green, and blue fine metal masks RFMM, GFMM, and BFMM corresponding to the red, green, and blue sub-pixel areas R, G, and B.
Referring to FIG. 2, the respective red, green, and blue fine metal masks RFMM, GRMM, and BFMM have red, green, and blue patterns RP, GP, and BP corresponding to the sub-pixel areas R, G, and B.
First, a substrate (1 of FIG. 1) on which red, green, and blue sub-pixel areas R, G, and B are defined, is prepared (s1), and then red light-emitting layers (4 of FIG. 1) are formed using the red fine metal mask RFMM with the red patterns RP corresponding to the red sub-pixel areas R (s2). Successively, green light-emitting layers (5 of FIG. 1) are formed using the green fine metal mask GFMM with the green patterns GP corresponding to the green sub-pixel areas G (s3), and finally, blue light-emitting layers (6 of FIG. 1) are formed using the blue fine metal mask BFMM with the blue patterns BP corresponding to the blue sub-pixel areas B (s4).
That is, in the related art OLED display device, the respective light-emitting layers 4, 5, and 6 are formed in correspondence to the respective sub-pixel areas R, G, and B. In other words, the sub-pixel areas R, G, and B, 1:1, correspond to the light-emitting layers 4, 5, and 6.
However, the OLED display device does not meet the color coordinate standard ITU-R BT.709 (International Telecommunication Union Radiocommunication sector Broadcasting service Television.709) that represents the color reproduction range of high definition television (HDTV).
Generally, an OLED display device processes images according to the ITU-R BT.709, however, the processed images are transmitted based on the NTSC (National Television Standards Committee) which is an analog image standard, and the color reproduction range of the NTSC is different from the color reproduction range of the ITU-R BT.709.
The following Table 1 shows color coordinator values of the NTSC and ITU-R BT.709, based on coordinator values designated by the CIE (International Commission on Illumination) in 1931.
TABLE 1CIE1931x,yRed Sub-Green Sub-Blue Sub-pixel Areapixel Areapixel AreaStandardxyxyxyNTSC0.6700.3300.2100.7100.1400.080ITU-R BT.7090.6400.3300.3000.6000.1500.060
The color reproduction range of a related art OLED display device will be described with reference to FIG. 3 and Table 2, below.
FIG. 3 shows simulation results of luminescence spectrums of the red, green, and blue sub-pixel areas in the related art OLED display device, and Table 2 shows ITU-R BT.709 color coordinate values that represent the color reproduction ranges of the red, green, and blue sub-pixel areas of the related art OLED display device, wherein the color coordinate values of the ITU-R BT.709 are based on coordinator values designated by the CIE in 1931.
As shown in FIG. 3, a blue sub-pixel area (B of FIG. 1) has a luminescence peak at a wavelength of about 450 nm, a green sub-pixel area (G of FIG. 1) has a luminescence peak at a wavelength of about 550 nm, and a red sub-pixel area (R of FIG. 1) has a luminescence peak at a wavelength of about 630 nm.
Also, the color coordinate values of the red, green, and blue sub-pixel areas (R, G, and B of FIG. 1), as shown in Table 2 for the OLED display device, are significantly different from the color coordinate values of the ITU-R BT.709.
TABLE 2xyRed Sub-pixel Area0.670.33Green Sub-pixel Area0.190.75Blue Sub-pixel Area0.140.06
Accordingly, a related art OLED display device requires an additional algorithm and circuit for processing and converting an image having NTSC color coordinate values so that the image can be represented by ITU-R BT.709 color coordinate values, which leads to an increase of manufacturing cost.
Additionally, since the related art OLED display device does not satisfy the color reproduction range of the ITU-R BT.709 directly, it requires an additional algorithm for representing the color reproduction range of the ITU-R BT.709. Implementation of this additional algorithm also requires an accompanying circuit.